This invention relates to a polycyanoaryl ether and a method for preparing the same, more particularly, to a polycyanoaryl ether which is excellent in heat resistance, solvent resistance, flame retardancy and mechanical strength, and a method for preparing the same. Further, this invention relates to products employing the polycyanoaryl ether, that is, to a polycyanoaryl ether series resinous composition for molding; a polycyanoaryl ether stretched or oriented film which is excellent in molding workability or processability and, particularly, mechanical strength; reinforced resinous composition and thermoplastic resinous composition which are excellent in heat resistance, mechanical strength, flame retardancy and molding workability; and a laminated product which are excellent in heat resistance, flame retardancy, molding workability and chemical resistance.
In the prior art, polycyanoaryl ethers having various structures are disclosed (see Japanese Unexamined Patent Publication No. 14270/1972). This preparation method is a method in which a polycyanoaryl ether is obtained by reacting dinitrobenzonitrile with an alkali metal salt of a divalent phenol in a solvent. When resorcin is employed as a divalent phenol, high-molecular weight polymer cannot be obtained. Also, when a mixture of equal amounts of bisphenol A and resorcin is employed as a divalent phenol, the polymer obtained is not crystalline and has a problem that the heat decomposition initiating temperature is as low as 390.degree. C. and thereby it can be said to have a sufficient heat resistance with difficulty.
Accordingly, development of a polycyanoaryl ether which is sufficiently excellent in heat resistance, as a matter of course, solvent resistance, flame retardancy and mechanical strength has been strongly demanded.
Also, although these polycyanoaryl ethers have excellent mechanical characteristics and thermal characteristics, crystallization rate is slow, whereby there is a problem that it is impossible to make a molding cycle sufficiently short at the preparation of molded products by means of a heat molding such as an injection molding.
Further, the resins which are excellent in mechanical strength and heat resistance including the polycyanoaryl ether, have a defect in molding workability or processability due to such properties and fail of having properties satisfiable in all demands. Particularly, the fact that molding workability thereof is not good leads to a problem when these resins are formed into a film.
Furthermore, thermoplastic resinous compositions containing polycyanoaryl ethers are put into wide uses because of their excellent thermal resistance and mechanical strength. However, in recent years, with more widely expanding scope of uses of such resins, there are strong demands for the development of resinous materials endowed with further excellent thermal resistance and mechanical strength as compared with those of the prior art.
Also, in the field of thermoplastic resins, particularly engineering plastics such as polycarbonate, polyester, etc. since such resins are excellent in, for example, mechanical strength, heat resistance and electrical properties, they have been put into wide uses as materials for electronic and electrical instruments, mechanical parts, etc. With more widely expanding of uses in this manner, in regard to these materials, further excellent properties are demanded and also flame retardancy is strongly demanded, particularly, from a viewpoint of insurance of safety at the time of use. As a flame retardant in this case, there may be added and mixed, for example, a metallic oxide or a halogen compound. However, when the flame retardant as described above is added to and mixed with a thermoplastic resin, there occurs problems that a weight of the composition obtained is increased to a great extent and lowering in molding workability is brought about.
Furthermore, as the material for electrical and electronic instruments or mechanical parts, laminated products obtained by impregnating and curing a thermosetting resin into a cloth or a mat comprising glass fibers or carbon fibers have been well known in the art. However, in the manufacturing steps of the above laminated products, a solvent is used to bring about worsening of the working environment, and besides the step for recovery of the solvent employed is also required. Also, a long period of heat treatment is required for curing of a thermosetting resin.
In order to cancel the problems in the case of using thermosetting resins as described above, it has been proposed to use a thermoplastic resin which is excellent in heat resistance as the constituent material of a laminated product in place of thermosetting resins.
However, of thermoplastic resins to be used, for example, a crosslinked polyethylene is insufficient in heat resistance, a polytetrafluoroethylene is inferior in molding workability, and a polyphenyleneoxide is insufficient in heat resistance and chemical resistance, thus possessing respective drawbacks, and therefore they were unsuitable as the constituent resin of a laminated product in the field of uses wherein heat resistance and chemical resistance are demanded.